MEN OF MATHEMATICS Finally, the curvature which-Riemann defined, the processes which he devised for the investigation of quadratic differential' forms (those giving the formula for the square of the distance "between neighbouring points in a space of any number of: dimensions), and his recognition of the fact that the curvature/ is an invariant (in the technical sense explained in, previous/' chapters), al found their physical interpretations in. the theory of relativity. Whether the latter is in its final form or not' is beside the point; since relativity our outlook on. physical science is not what it was before. Without the work of Riemaan this revolution in scientific thought would have been impossible-; unless some later man had created the concepts and the mathe- matical methods that Riemann created.